Need help with clay modelling?

What kind of clay did you buy? If it is an earthen clay, take it back. It has to be fired in a kiln and needs special treatment to create figures with it.

If you bought non-hardening clay you just warm it in your hands by kneading it, then you shape it into the players you want.

There is also an air-dry clay I haven't used, so you'd have to read the instructions on it.

Polymer clay such as Sculpy and Fimo are hardened in your home oven (NOT a microwave or toaster oven). You knead it until you can work it into the shapes you need, then follow the directions for baking it.

Along with Jeanne's advice.

How large will these sculptures need to be? How tall would your standing soccer player be?

If only 2-3 inches tall, use Polymer clay (FIMO), SCULPEY,etc) without an armature(wire simple skeleton).

If more like 6 inches tall, you'll need a lot more clay and you may need to use wire armatures and then put your clay onto those before shaping or carving details. Leaving wire sticking out of the bottom of the feet allows you to use that wire to bind the players to a surface to stand on. I guess you could just glue the feet to the surface.

Great info at Squidoo for using polymer clay and how to make armatures, simple and complex. http://www.squidoo.com/armatures